As this type of conventional hand, there is known a hand which has a main body in which guide grooves are formed, a pair of sliders, and a pair of gripping members (for example, refer to Patent Literature 1). In this hand, the pair of sliders are arranged linearly movable in the guide grooves in the opening/closing directions and the pair of gripping members are attached to the pair of sliders. The pair of gripping members can be driven by a drive source arranged in the main body such that the gripping members are moved in the opening/closing directions. When the pair of gripping members are moved in the closing direction (that is, when the pair of gripping members are moved closer to each other), the gripping members can grip a substance, while, in contrast, when the pair of gripping members are moved in the opening direction (that is, when the pair of gripping members are moved to separate from each other), the gripping members can release the substance
A mechanism for moving the pair of gripping members in the opening/closing directions is structured as follows. A disk cam is attached to an output shaft of the drive source. As shown in FIG. 9, a pair of cam grooves 71a are formed in a point symmetry on the disk cam 71. A pair of pins 72 attached to the pair of sliders are fit in the pair of grooves 71a. In response to rotation of a rotating plate serving as a driver, the pair of pins 72 which serve as followers are caused to slide in the pair of cam grooves 71a, which makes the pair of gripping members move linearly in the opening/closing directions. The cam grooves 71a can be formed linearly in the radial direction as shown in FIG. 9 or can be formed in a spiral shape.